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Appendix D
3

Appendix D

Appendix D

(OP)
Does anyone else view appendix D as a poor code?

Let's take a poll;
How many people use a simpler, or older anchor design routine?
How many people actually use Appendix D?

RE: Appendix D

Appendix D is required.

RE: Appendix D

I sorta just guess....

Well, really - I'm trying to use App D - as soon as I write a spreadsheet to do it (best way to learn it).  Until then I use the ASD bolt table in the IBC.

RE: Appendix D

A guy who worked at my office before I did wrote a spreadsheet on Appendix D as his masters report.

In other words, it's not that simple.

RE: Appendix D

Sure it's tougher than older ways.  Anybody's welcome to come up with a better alternative and argue for its adoption.

There are those around here who are VERY vocal wrt App. D, but when asked for specific examples of unreasonable results, we hear crickets.

RE: Appendix D

Spreadsheet is the obvious way to go for this. I haven't gotten unreasonable results, but it is just the fact that in order to design a couple of bolts embedded in concrete I must to go to a spreadsheet -unless I want to spend a couple of hours to make sure it is exactly correct according to App. D for anything but a simple bolt pattern. .... seems a little unreasonable.

RE: Appendix D

Agreed haynewp, but this is true for many things.  Wood connection design with all those crazy factors comes to mind.  Heck, calculating phiMn for an unbraced steel beam takes a good while without tables or a program.

What I'm still waiting for (and maybe it does exist) is for someone to come up with a connection for which App. D gives irrational results as compared to the old ways.

RE: Appendix D

I don't view it as a poor code.  It is a little awkward and slow to use, especially if you haven't used it before.

The limitation on bolt size applicability is irritating.

RE: Appendix D

Let's turn it around:
Who has experienced a problem (failure) based on the way we used to do it?  i.e. ICBO reports, PCA Methods, UBC Anchor bolt allowables, etc?  

RE: Appendix D

I respectfully disagree, Jed.  There are factors of safety and the low probability of the worst case design load being on there.  No failures doesn't prove anything.  Matching up test results with the equations is the way to go IMO.  Honestly, I haven't done this with App. D, so don't know whether it's better or not.  I assume it is because that's what the ACI folks were probably looking at when they adopted it.

RE: Appendix D

I've read a lot of the background material. App D is much closer to test results than older methods.

RE: Appendix D

Ok a few thoughts.

In the old method, by just using guides in the manufacturer's catalog, there were factors of safety, and all sorts of reductions due to edge clearance and bolt spacing.

In the new method, we are using results which more closely relate to the actual failure point, for a PERFECTLY installed anchor.

This last point is the part that scares me. How many times have anchors been installed incorrectly on your job? Are the holes really cleaned with compressed air and wire brushed out? What if they aren't? How does that affect the values you get? With the old method, it appears to be safer. And really, most jobs that use post-installed anchors, cost of the bolts/plates aren't going to make/break a job. I don't understand why we need to be so exact on these anchors...

Just my 2 cents even though we're being forced in App. D now.

RC
All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke

RE: Appendix D

JedClampett and RCraine:

I couldn't agree more! Appendix D has always looked like a solution in search of a problem to me. The old method did work. And it kept us out of trouble.

Its easy to calculate exactly how many anchors and what size to use when your in a testing lab, and the installation is being constructed by grad stutdents in a very controlled enviroment, and it won't every be used in a real building anyway. Its a lot harder to go to the very edge with your design when you know its going to be installed by a worker on a real job site in the rain, or cold or heat, and he is in a foul mood, and its getting close to quitting time on Fridaym and he's not following every instruction to the letter. And if he screws up, and it falls down, You might have just lost your company and everything you spent 20 years building.

I don't mind that there was a little bit extra factor of saftey built into the old way. Don't mind it one bit!



The n

RE: Appendix D

RCrane, you have some good points.

The last time I checked, though, App. D wasn't used for adhesive anchors, so that leaves only expansion anchors and embedded studs or rods.  The issues you mentioned don't exist for most of those.

Right or wrong, "ease of manual calculation" will NEVER be a criterion for deciding if an equation is used.  There are LOTS of examples of modern provisions that are inconvenient (or worse) for manual calcs.  Almost anybody regularly using App. D, the wood connection heinous equations, AISC Ch. F, AISC stability design provisions, etc. will use either a program or a table.  I really don't like some of this, but that's obviously the way it's gonna be from here on.

RE: Appendix D

Similiar problems do exist with mechanical anchors. The holes for Undercut and Expansion anchors are supposed to be cleaned out with compressed air according to Hilti.

I've seen expansion anchors without nuts on them, or nuts that did not come in contact with the surface.

Problems do exist with the installation of mechanical anchors. Thats why a bit more factor of saftey was never a bad thing in my mind.

RE: Appendix D

271828,
Expansion anchors can be installed wrong. If they aren't tightened  to the correct torque or the hole isn't cleaned out correctly. I have no problem with the amount of work, its the thought of why do we need to design so tight on items that could use a factor of safety anyways.

RC
All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke

RE: Appendix D

Thank you all for covering my back.  I have no doubt that Appendix D more accurately simulates anchor behavior.  But part of code writing is translating the test data into usable code guidance.  There are a lot more accurate simulations for bending moments, torsion, corbel design, redistribution of moments, etc.  But someone decided that the models needed to be simplified or they wouldn't be used.  If a code is too onerous, it won't be used and then what has been accomplished?

RE: Appendix D

deadhorse

RE: Appendix D

Some of the post-install bolt manufacturers have software that does the App. D calculations.  e.g. Simpson & Hilti.

RE: Appendix D


Acutally, one of the big changes with this code is that mechanical and adhesive anchors must now be tested with the anchor installed incorrectly on purpose.  This is a major upgrade over the old method which assumed the anchor was installed perfectly.  You get a different phi factor depending on how well the anchor works installed correctly vs. incorrectly and get a rating 1 through 3 which again corresponds to different phi factors.  If your anchor works good installed correctly but performs like crap when installed incorrectly you get nailed on the phi factor.  This testing never existed before.  Manufactures are now going to highlight anchors with a category 1 rating, the best possible/least sensitive to installation.

RE: Appendix D

PackerFan,
Thanks for the information on the other forum, however, I disagree with you here. Hilti's HDA Undercut anchors is given a 1 for anchor category, as you mention above for least sensitive to installation. These bolts are all metric right now. If the contractor doesn't use the correct tool, bit and setting tool for this installation these bolts are useless. I was on a job where the Hilti representative (field engineer) came out to review the installation due to concerns the contractor would do it incorrectly, both on EOR's end and Hilti's.
What company is going to put out a bolt that isn't in category 1?

It doesn't seem to make sense to me but thats just my opinion.

RC
All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke

RE: Appendix D

I feel not having problems over a long period of time is very significant. In my opinion this is another case of the undue influence of out of control academics on the code process.

There are several things that are not exact models of physical reality but have worked for an extended time such as the equivalent frame method for slabs. I use the PCI method which is in their manual. At least it is presented in a usable manner.

RE: Appendix D

ron9876, I won't belabor the point beyond here because we've gone over it before and it's always a big fight.

The bottom line is that ANYBODY can come up with design provisions, be on committees, etc.  If someone doesn't like how it's going, then he or she needs to step up to the plate and stop it.  Otherwise, it's like someone who doesn't vote, but complains about what politicians do.

RE: Appendix D

"not having problems" can be deceptive.  Anchor bolts that are designed for wind or seismic loading can be there for decades and never be loaded to their design loading.  I do seem to recall a recent tunnel-roof failure due to dead loads on a bolt, though.

RE: Appendix D

Well it certainly is true that many structural elements never get fully loaded. But the precast industry has used headed studs to carry gravity loads for years. My point is that between engineer errors and contractor errors if there is something that we use that has a problem it will show up like corbel design has.

As far as code development is concerned there is no way that I have time or money to spend on committes. But it does seem to me that in about the last decade that we have had code development and revision at a runaway pace. Especially in the concrete code. For me it is really frustrating due to the lost time and money spent. I think Appendix D is an excellent example of a change for the sake of change. It was simple and it did work. Load testing indicated that the previous method worked fine so why buy new literature and try to fight thru a cumbersome (to be polite) design procedure when it wasn't needed.

RE: Appendix D

ron9876:

Thank You for saying what most of the structural engineers I know really think about Appendix D!



RE: Appendix D

RON9876 - I don't think that testing indicated the previous design worked fine.  At minimum, the old method had a horrible correlation between expected and tested results.  These are the reasons they tried to come up with a new method.  I try very hard to avoid the app D method because it is cumbersome.  Hopefully, it improves with code revisions.

RE: Appendix D

You make good points, ron.  Hard to argue with most of them.

A little more about code development and academics, though:

The professors I know who are active on committees do this stuff almost as hobbies.  They've studied a particular subject to death and are interested in it.  They don't have time either, but do it anyway because it's fun and interesting.  I really don't see why design professionals don't do this also.  There's really very little work involved and meetings are only a couple of times per year in most cases.

For what it's worth, tenure and promotion are the ultimate goals of professors.  Code provision adoption has *very* little impact on this.  Dollar amount of externally funded research projects is the deciding factor by a very wide margin.  They *say* that journal papers are also, but that's lip service.  The universities want money.

I serve on one very significant committee and professors are only 20% of the group.  They have an impact for sure, but they are far from overwhelming all the designers, fabricators, etc. in the room.  I'm sure there are counter-examples out there.  

Get in there and fight it out!

RE: Appendix D

I have an idea, in all seriousness.  Not being sarcastic.

If some of you guys have studied App. D enough to judge it, then why not come up with a simplified version?  Make some conservative assumptions, show when some limit states won't control, etc.  I bet this method could be boiled down to something useful without a tremendous amount of effort.  Write it up as a journal paper.

There's obviously enough interest and energy to get this done.  Heck, maybe I'll do it myself, LOL.  I'm actually a bit surprised that this hasn't been done already (perhaps it has).

RE: Appendix D

Guys as I said above check out how the PCI Handbook presents this information. It is similar but for me it is much easier to follow and use.

RE: Appendix D

Attached is my version of a very workable method of selecting expansion anchors. It is used in a country where the structural code committees might actually allow practicing structural engineers to make a decent living.
For that reason, the identity of the country cannot be revealed.

This method has been used for years and years with nary a problem.

What do you think? :) :)

RE: Appendix D

(OP)
Ha ha.  Design tables are fine, but not fully parametric.

And, OK, Appendix D is not that bad, but it requires a program.

So, does anyone have an open source program to share?

RE: Appendix D

If you limit the scope of application, it's not too hard to come up with a spreadsheet for App. D.  For example, if you always have the same bolt pattern and the same shape of concrete face, you can deal with it.  But trying to generate a spreadsheet that works for any bolt layout whatever and any concrete shape whatever would be a bit of a trick.

In the case of the table above, you can generate something like that if you use the same bolts all the time, limit the spacing in various ways, etc., but I've never seen a table like that that would work for any bolt anywhere.

RE: Appendix D

271828,
"No failures doesn't prove anything."
COME ON!!!!!!!!!!!!!!!!!!

The precast industry has not had buildings falling down around us everyday.  That is the true test. A laboratory is only a simulation.  Have you ever been to Rome.  Maybe we should chastise the Romans for their building practices since they didn't have test reports before building say the Coloseum or the Pantheon.  There is something to be said for experience.  This is one arena where the Roman engineers would be laughing at us.  

Another example is Pre-engineered metal buildings.  They don't collapse from anchor failures. Go to an older pre-engineered building and look at the size of the pier the anchor rods are embedded into, usually 18x18 or less. That pier if design by App. D would be 2'-6" x 2'-6" or more.  Come on!!!!  The results from Appendix D do not match what we see in the field. Certainly, some of those structures are not seeing the full design load but I dare say most are!  I have not reviewed how they are testing these anchors but it seems to me that the results are way too conservative.

Then the time it takes to calculate by hand...
Come on!!!!!!!

Go ahead and try to write a spreadsheet for ACI APP. D.  You need a PhD in Excel.  It would probably be better to write it in Visual Basic, patent it and sell it to all of us hapless engineers.

App. D comes from the Euro Code. Take one look at the EU's bloated constitution and it's not a far stretch as to why App. D looks the way it does.

RE: Appendix D

vincent, LOL on the hyperbole.  These forums are too boring otherwise.

I'm not being sarcastic--totally serious: You and some of the other guys who feel very strongly about App. D. really need to get together and come up with a better way.  I wholeheartedly believe it is possible.

One fast option would be to simply accept that the equations better predict the behavior, but are more complex than necessary.  Then look critically at which limit states never control or only control in rare cases.  Re-formulate the provisions into something easier to use, although probably a little conservative.

IF App. D is unreasonably conservative for some limit states, then figure out why and use another model or equation!  This ain't rocket science.

Write it up as a simplified method and get it published in a journal.

"Don't have time, but academics do." is a sorry refutation of this idea, IMO.  I've spent enough time around professors to see how the good ones do things like this.  They do craploads of stuff like this on their own time.  It's more like a hobby that spawns off some sponsored project that provides them with test results (but does not have the goal of Code provision development).

If there's not enough interest and energy to try and fix the problem, but IS enough interest to complain, then, well I don't have anything helpful to add (Mama said not to say anything if I couldn't say something nice, right?) -- LOL.

RE: Appendix D

The former PCI method which used the 45 degree theory is my recommendation. Performed just fine and didn't waste nearly as much time.

RE: Appendix D

ron, how do you conclude that it performed just fine?

Does anybody here really know WHY App. D was developed and adopted?  Who sponsored the research?  Why?  Did some guy just come up with this stuff for the fun of it?

RE: Appendix D

This program has limitations (single, two or four bolts only) but can be a useful "learning tool". http://www.simpsonanchors.com/software/anchor_design.html

Hopefully engineers don't use this "tool" as a black box, until they get a full grasp of each governing case.

As much as I have my gripes about Appendix D, the concept is really quite simple.  Get the factored sear and tension, get the governing tensile and shear strengths (using all the modification factors for spacing, edge, etc), then do the interaction.

RE: Appendix D

I read it in different publications. It is my understanding the new method was developed to be more consistent with test results (+/- 22 degrees vs. 45 degrees).

The new method IS much more cumbersome and IS time consuming. I think that the code development industry has lost sight of the best interest of the people that use the design codes. Especially the concrete codes.

RE: Appendix D

ron9876:

Couldn't agree more!

Does anyone really use Appendix D on real structures? Or has everyone, like me, just developed simplified 'work arounds' that we know are conservative, but we use to get the work done without wasting too much time?

RE: Appendix D

"Does anyone really use Appendix D on real structures? Or has everyone, like me, just developed simplified 'work arounds' that we know are conservative, but we use to get the work done without wasting too much time? "

That's exactly what I'm typing about.  Rather than being hurt my App. D, you came up with a better way.  It's probably a small step to develop something like this into a formal simplified procedure and publish it for all to use.  Then the problem seems to vanish.

RE: Appendix D

I'm currently writing a spreadsheet for use based on appendix D and so far it doesn't look too bad.  Certainly not requiring a PhD.  But some limitations I've put on it will be necessary (i.e. only cast-in anchors, only tensile plus ONE lateral load - i.e. no x and y forces laterally -just one direction)...that kind of thing.

I think a lot of Appendix D reaction is based more on Who moved my cheese" than anything else.  There has always been, and will always be, resistance by engineers to changing design methods as it threatens our self-knowledge and security when we suddently can't design per code because of a newly percieved code provision.  After you get into it a bit the fear and loathing go away rather quickly.

But I do remember my old mentors designing concrete based on a 1950's era method...in 1985.

RE: Appendix D

Overall Appendix D is an improvement.  One can now actually understand what failure mode is controlling there design.  With this knowledge and engineer can more accurately evaluate the risk, the approach taken, alternative designs, etc.

My gripe is with the symbols. Its like the committee members got in an argument. Some wanted lower case.  Some wanted capitols, and some wanted greek.  So they compromised and used all three for each symbol.  Its hard to tell when reading it when one symbol begins and one ends.  

That said I was able in about a day to write a really good excel sheet for a joist embed connection to the top of a concrete tilt-up panel or concrete wall tie beam in about a day.  

Cavemen could have come up with better symbols than these guys.   They could have used the symbols above the numbers on the keyboard. They could have used F1, F2, F3, F4, etc...  Anything would be better than what they've done.  

On codes and specs.  I we should lobbie congress for a special law to jail specification writers who want to put out a new code or spec every two years.  Everytime I just about get a good feel for a new code they decide to change.  Now good ole steel is $!@#^$# me.   

See how convenient those symbols above the numbers on the keyboard are!

RE: Appendix D

(OP)
Ok, I've found my cheese again.  Handcalcs done in 10 minutes.  It would still be nice to have a program.  Open source freeware anyone?  anyone?  Bueller.

RE: Appendix D

Sorry to resurrect an old thread, but I was hoping I could shed a little light on why (at least) engineers in high-seismic areas are unhappy regarding ACI 318-05 Appendix D.

The biggest reason has to do with The D.3.3 section.  D.3.3.3 takes 25% of your strength away off the top in medium- and high-seismic areas.  D.3.3.4 and D.3.3.5 then require that a ductile steel yielding failure must govern.  The CA Building Code has modified this to state that where steel yielding doesn't govern, you have to multiply your applied forces by 2.5.

This means that the anchorage condition which will often govern is a (low) concrete breakout value, reduced by 25% and then forced to cope with 2.5x the design forces.  (I haven't personally dug into the concrete breakout calculations too deeply for situations other than sill anchor bolts, but my impression is that they are broken for some cases.)

For example, this means that a 5/8" anchor bolt with a 1.75" edge distance, which was worth ~1500 lb. under ASD in the previous CBC, now ends up being worth the equivalent of 285 lb.  Yes, 285 pounds...that's not a typo.  And 562 lb. for a 2.75" edge distance.  The wood isn't even close to governing.

As you can see, it's not just that Appendix D is a hassle--hassles can be dealt with.  But I think anyone looking at the massive drop in allowable values would admit that something needs fixing, at least for certain situations.  Changing the ductility requirements and reviewing the shear-parallel-to-an-edge breakout values would be a good start.

Hope this helps...

Bret

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